Aaron Sorkin’s directorial debut arrives and it’s certainly a heady concoction, full of fizz and invention, but it does end up feeling just a little hollow. It’s the true story of the improbably-named Molly Bloom, whose career as a professional skier is interrupted by an injury and who ends up making more money running her boss’s poker game than she does doing her job. She therefore takes the game away from him and ends up as the unwitting confidante of a number of top players, including members of the Russian Mob.

Sorkin borrows a page from his own Facebook, designing the structure of the film around Molly’s court case, in which her phones full of incriminating texts from regulars at her poker games become the prize which law enforcement is after but which Molly, despite protestations from her lawyer, is unwilling to surrender. Around this main narrative thread, there are frequent flashbacks to Molly’s childhood, young adulthood and evenings running poker rooms.

The two different parts of the movie are handled very differently. Especially early on, Sorkin makes the flashbacks an assault on the senses. Chastain rattles out Sorkin’s voice-over dialogue with crisp authority as driving music knits together images from a huge variety of sources, to the point where the style is not so much Award Winning Prestige Motion Picture, but more YouTube video. At times, he seems about to fall prey to one of what David Frost called “Lord Privy Seals“.

The rest of the film – mainly contemporary verbal fencing between Jessica Chastain’s resolute Molly and Idris Elba’s compassionate lawyer (thankfully much more cautious Stringer Bell than lumpen Luther) – is more conventionally shot and edited. Sorkin, whether wisely or not, trusts that his dialogue and his actors will carry the day. And they mostly do. Both Elba and Chastain do solid work, if a little one-note. Kevin Costner and Jeremy Strong are both fine. Michael Cera has fun as movie-star composite Player X, and Chris O’Dowd possibly has little too much fun as the hilariously inarticulate Douglas Downey, whose Russian Mob connections prove to be Molly’s downfall. It’s just a shame that as a director, Sorkin hasn’t found any middle ground between shooting his scenes like a particularly demented music video on the one hand, and like any random episode of The West Wing on the other.

The story itself is well-paced and never less than entertaining. Sorkin uses the backstory well, serves the needs of poker and poker-related gamesmanship, family drama and legal thriller equally and adroitly, and – as you might expect – the dialogue crackles along. He is also unafraid to deploy jokes, even during moment of the highest drama, so when Elba is speechifying or Chastain is expositing, all is right with the world.

But there are a few niggles. Surprisingly, not all the poker stuff is completely accurate. Twice Sorkin, who must have known better, over-reaches. Wanting to establish Michael Cera’s character as a brilliantly player who can force better hands to fold, he gives the other player the nuts, i.e. an unbeatable hand, which strains credulity quite unnecessarily. Later, he allows Molly to begin raking the pot in the middle of a hand, which is highly unlikely to be true. I suppose it could be, I haven’t read the book, but most players would revolt at this sudden, unexpected and irrevocable rewriting of the rules.

Ultimately, with an eye on the Oscars, the question becomes – is this just a thrill ride, a roller coaster of words and situations, or does it illuminate something bigger than itself. In conversations with Dad Costner and lawyer Elba, the nature of Molly’s stubborn integrity is probed, but she remains a movie hero, who plays by her own rules, but whose interior life is only glimpsed occasionally, unless it’s being spelled out for us in voice over.

And as the film has no ambitions to explore anything beyond the realms of poker and crime, this remains a well-made entertainment rather than a masterpiece.

Look out for episode 0 of my new podcast Best Pick, dropping on Wednesday, and be back here on 23 January for the Oscar nominations,